Chock release



July 7, 1959 -A. w. DUNCAN CHOCK RELEASE s sne'ets-'sheez 2 Filed oct. 7. 195s July 7,1959 Az'w. DUNCAN 2,893,679

CHOCK RELEASE Filed oct. 7. 1955 3 'sheets-sheet 5 /rE/vrwv l lUVM/.sr )VELLEmayu/vcfw mwa, s @ma United States Patent CHUCK RELEASE Angus Wellesley Duncan, Leigh Sinton, near Malvern,

England, assignor to The Mining Engineering Conipany Limited, Worcester, England, a British company Application October 7, 1955, Serial No. 539,227

Claims. (Cl. 248-351) This invention relates to a new or improved chock release for use lin conjunction with roof supports in coal mines and other underground workings.

Chocks as used for roof supports are commonly built up from timber baulks in the form of a hollow square with or without a fabricated steel base. The chock is tightened between the floor and the roof by means of wedges driven in near the roof, and to allow the chock to be withdrawn one layer of the structure is formed by chock releases which can be released to collapse the whole chock. Such chock releases commonly comprise four Vpairs of Wedge members located at the corners of the chock structure and retained in operative relationship by quickly releasable catches. The angle of the wedge member is normally such that there is a tendency to collapse of about of the roof weight supported by the chock, and that is the load taken by the catches.

In one known form of chock release the catch is a latch member pivoted in the lower wedge member of a pair and having a T head which passes through a slot in and bears against the vertical face of the upper wedge member. To release the chock the operator strikes the heads of the latches for each of the pairs of wedges upwardly with a long handled hammer so that the upper wedges are released and are free to slide downwardly and outwardly over the lower wedges, the upper wedges being attached by chains to the assembly to retain them when collapsed.

There are various other forms of chock-release but all of them incorporate double wedges with some form of catch which has to be moved under high and progressively increasing load per unit area to effect release.

Among the practical disadvantages of known forms of chock release are that the elort required to release the latches may be diicult to apply in thin seams and may require the operator to be in a dangerous position, that when wear of the co-operating faces of the wedges and latches takes place the wedges may self-release unless very carefully set and the release of one pair of wedge members may cause the others to self-release with the operator in a dangerous position, and under heavy loady explosion.

According to the invention, in a chock-release comprising a pair of co-operating wedge members of which one is adapted to slide on the other for release, relative sliding movement between the Wedge members is normally prevented by a transverse key of substantially semicircular cross-section mounted for angular movement in a recess in the inclined surface of one wedge member with a portion of its at face projecting from that surface for engagement with a transverse abutment on the co-operating inclined surface of the other wedge member, in combination with releasable locking means for holding the key against angular movement.

The wedge members have an angle above the friction angle, that is, there is a component of the vertical load ice on the chock tending to cause the one wedge member to slide on the other, and this force is resisted by the key which, in its locking position, prevents relative sliding movement between the wedge members.

When the locking means are released the key is free to be turned by the force acting on it into an angular position in which it lies wholly within the first wedge member and the one wedge member is then free to slide on the other to release the chock.

In a preferred practical construction the key is formed by a cut-away portion or portions of a shaft journalled in the upper wedge member with its axis in or adjacent to the plane of the inclined surface of the member, and in the load-sustaining position the flat face of the key lies substantially at right angles to the inclined surface of the wedge member and the projecting portion of the at face of the key engages with an abutment on the lower wedge member substantially at right angles to the inclined surface thereof.

An arm or lever is preferably fixed on the key shaft and is adapted to be held in a position corresponding to the load-sustaining position of the key by any convenient form of readily releasable locking device. An arm or lever may be mounted on one or each end of the key shaft or it may be mounted centrally on the shaft and work in a slot in the lower wedge member.

The major proportion of the sustaining load on the key is taken in journal reaction on the key shaft and a minor proportion is applied to the key as a torque which tends to rotate the key shaft about its axis and is resisted by the arm or lever and its releasable locking device. For the stated reasons, this torque should be as low as possible, i.e. large enough but not much larger than necessary to overcome the prevailing friction of the parts when the locking device is released so that the turning of the key is ensured.

The proportion of the sustaining load applied to the key in the form of torque can be varied by selection of the distance from the axis of rotation of the key at which the abutment face on the second wedge member engages the projecting face of the key. As the torque should be low, the mentioned distance should be as short as admissible.

This variation may be effected by means of an appropriate radius `on the edge of the abutment face on the second wedge member, the axis about which the key rnoves angularly lying in or closely adjacent to the inclined surface of the first wedge member.

It wil-l be appreciated that as soon as the locking device is released the journal load on the key disappears and the only sliding pressure between the key and the abutment face on the second wedge member is that required to accelerate the angular movement of the key and its associated arm or lever.

The loose wedge member may be secured against loss by a chain or the like or in any other convenient manner.

The improved chock release is economical to manufacture and is simple to set and release while being free from any risk of self-release under load.

Further, as there are no parts moving under heavy loads during release the risk of sparking is eliminated, and as the release can be effected from a distance, risk to the operator is reduced to a minimum.

One practical form of chock release in accordance with the invention is illustrated by way of example in the accompanying drawings, in which:

Figure 1 is a longitudinal vertical section of the chock release on the line 1-1 of Figure 2;

Figure 2 is a transverse vertical section on the line 2 2 of Figure 1;

Figure 3 is Va longitudinal horizonal section on the line 3-3 of Figure 1;and

Figure 4 is a fragmentary horizontal section showing the locking means in the released positions.

The 4chock release illustrated jcomprises a lower wedge member and an upper wedge member 11 adapted when freed to slide downwardly and outwardly on the lower wedge member-and Vso to release the chock.

vNormally the upper wedge member is held in the load-substaining position illustrated by the releasable 'means forming the subject of 'the invention.

A transverse shaft 12 is journalled at its ends in the upper wedge member adjacent to the inner end thereof with kits axis parallel to but spaced a short-distance above the plane of the inclined face 13 of the wedge member. This is clearly vshown in Fig. '1 where the axis of the key is designated'by'a and the mentioned short distance is Aindicated by d. Portions of the shaft on each side `Vof the centre of its length are cut away for lengths equal to the width of the parts 14 ofthe lower wedge member on which the upper member slides, 'these portions of the `shaft being of'semi-circular'cross-section to form a key. Normally the at face 15 of the key `is substantially at right angles or within a few degrees of right angles to the cc-operating inclined Isurfaces of the wedge members so that aportion of the key projects into a recess in the inclined surface of the lower wedge member for engagementwith a'transverse abutment 16 on that member inclined at the same angle as the flat face of the key.

When the assembly is `under 4load as part of a chock supportinga mine :roof or the like'there is a component ofthe vertical load tendingto cause the upper wedge member to slide downwardly and outwardly on the lower wedge member, and as the key is engaged by the abutment 16 on a line spaced from the axis of the key this force tends to cause rotation yof the key in a clockwise direction in AFigure l.

Angular movement'of the key is normally prevented by an arm 17 intergral with or rigidly xed to the centre of the key shaft 12 and extending vertically downwards through a slot in the lower wedge member between the parts 14. The lower end of lthe arm engages the flat face 18 of a cut-away central portion of a locking shaft 19 journalled inthe lower wedge member adjacent to its inner end. The lower extremity of the arm engages the face 18 at a point slightly above the axis of the locking shaft so that the load component tending to rotate the key shaft 12 in a clockwise direction applies through the arm 17 a force tending to rotate the locking shaft 19 in an anti-clockwise direction.

For holding the locking shaft 19 against angular movement one end 20 of the shaft which projects laterally from the lower wedge member is made of hexagonal cross-section. A sleeve 21 of hexagonal cross-section is a sliding iit on the part 20 of the shaft and the inner end of the sleeve is normally located in a hexagonal recess 22 in the sidewall of the ywedge member to hold the sleeve and locking shaft against angular movement.

The sleeve 21 is held inthe locking position by the bolt 23 of a D link 24. The bolt passes transversely through the sleeve and through a longitudinalkeyhole slot 25 in the shaft. The central part of the bolt is formed with two opposed flats 26 and lies inthe wider inner end of the slot 25, as shown more particularly in Figure 2, the bolt being retained in this position by the D link hanging in a vertical position under gravity.

When it is desired to release the chock a chain or `cable is attached to the D link which is swung up into a hori` zontal position and drawn outwardly. This withdraws the sleeve 2l from its recess as shown in Figure 4 and unlocks the shaft 19. That shaft is then free to rotate under the force applied to it by the end of the arm 17, and as soon as the ilat face 18 reaches the horizontal'plane the lower end of the arm can pass it. This allows the key shaft 12 to rotate until the key portions 1S lie wholly within the upper wedge member which is then lfree to slide downwardly and release the chock.

To prevent loss of the upper wedge member the lower end of the arm 17 is provided with laterally projecting lugs 27 of a width greater than that of a slot 2S in the outer wall of the lower wedge member, so that the upper wedge member is allowed to fall clear as the arm can pass through the slot but is kept attached to the lower wedge member.

The proportion of the sustaining load whichris applied to the key shaft l12 as torque can be varied by variation of the distance from the axis of lthe Yshaft at which-the flat key face 15 is engaged by the abutment 16. The edge of the abutmentis provided witha radius )'30, seen in Figure l, and by increasing this radius the leverage through which the torque acts on the shaft will be increased.

The central part of the key shaft 12 may be provided 'withY a radially projecting lug 31 working in'a'part annular vrecess 32 inthe upper wedge member to vlocate the 'key shaft against appreciable axial movement.

Y YOne end of thekey shaft 12'may'be squared as shown at 33 or otherwise formed for engagementbyatool when `re-settingthe chock'release.

Apair of wedge members as 'described above will usually be associated with an opposed 'pair to form a unit replacing acho'ckpiece, the lower wedge'members of the two pairs `being rigidly connected 'by plates 34 bolted'to them.

In sucha Ystructure there may be a separate releasable locking means for the'key shaft of e'ach pair of wedge members or there may tbe a common locking device. For example a locking'shaft such as `the shaft 19 might be journalled in the 'structure midway 'between vthe wedge members and arms fixed on the keyfshaftsof the wedge members could engage with opposed flat in the'locking shaft.

I claim:

'l. A 'chock release incorporating upper and lower wedge members having oppositely inclined surfaces vin 4sliding engagement 'with each' other'and having means for with said recess and including a key portion of semicircular cross-section located in said'recess and provided with a at diametrical face, a 'transverse abutment in the inclined surface of the lower wedge membenand releasable locking means'for holding saidike'y shaft'in an angular position in whichapart ofthe flat face of said `key portion projects from the inclined surface of 'the upper Wedge member for engagement by the abutment 'in the lower wedge member, said locking means comprisingan Iarm on said key shaft, a 'locking shaft parallel to said key shaft and journaled in the lower wedge member, said locking shaft including a lsecvondkey portion of semi-circular cross-section with a ilat diametri'cal face, the vfree end of said Varm engaging the flat face of said second key portion at a point spaced from the axis of the locking shaft, `and releasable means for holding the locking shaft against angular movement. j

2. A chock releaseas in claim l, whereinthe releasable means for holding the locking shaft against angular movement comprise a sleeve s'lidably keyed on said locking shaft and normally engaged with the lower wedge member, and a releasable locking device for normally holding the sleeve against axial movement on the locking shaft, said locking device being held in the locking position by gravity and being releasable Yfrom a remote point.

3. A chock release as in claim l, wherein the releasable means for holding the locking shaft against angular movement compris@ hexagonal end portion of said locking shaft, a hexagonal sleeve slidably keyed on said end portion, a hexagonal locking recess in the lower wedge member in which the inner end of said sleeve is normally engaged, a longitudinal keyhole slot in said end portion having its wider end nearest to the wedge member, opposed holes in the sleeve registering with said wider end f the keyhole slot, a D link including a bolt passing through said holes and slot, said D link normally hanging vertically under gravity, and flats on the portion of the bolt within the keyhole slot permitting the bolt to be moved into the narrower end of the keyhole slot and withdraw the sleeve from the locking recess in the wedge member when the D link is swung up into a horizontal plane.

4. A chock release incorporating upper and lower wedge members having oppositely inclined surfaces in sliding engagement with each other and having means for normally preventing relative sliding movement between the wedge members comprising a transverse part-cylindrical recess in the inclined surface of the upper wedge member with the axis of said part-cylindrical recess being closely spaced from said inclined surface, a transverse key shaft coaxial with said recess and having a key portion of semi-circular cross-section located in said recess and provided with a flat diametrical face, a transverse abutment in the inclined surface of the lower wedge member, bearings in said recessed wedge member for the ends of said key shaft whereby owing to the recess axis being closely spaced from said inclined faces the major proportion of the load on the key being taken by said bearings and a minor proportion is applied to the key as a torque about said axis, and releasable locking means for holding said key shaft in an angular position in which a part of the at face of said key portion projects from the inclined surface of the upper wedge member for engagement by the abutment in the lower wedge member, said releasable means comprising an arm located centrally on said key shaft and extending downwardly therefrom, the lower wedge member being provided with a longitudinal slot through which said arm extends, releasable means in the lower wedge member for engaging the lower end of said arm to hold the key shaft against angular movement, and

laterally extending lugs on the lower end of said arm of a width greater than said slot for preventing loss of the upper wedge member when released.

5.I A chock release incorporating two co-operating wedge members having oppositely inclined surfaces in sliding engagement with each other and having means for normally presenting relative sliding movement between the wedge members, said means comprising a transverse part-cylindrical recess in the inclined surface of one wedge member with the axis of the recess closely adjacent to the inclined surface thereof, a transverse key shaft journaled in said recess and having a key portion of semi-circular cross-section with a at surface on one side and a semicylindrical surface of the same radius as said recess on the other side, bearings in said recessed wedge member for the ends of said key, a transverse abutment in the inclined surface of the second wedge member and having a flat surface substantially at right angles to said inclined surface, and releasable locking means for holding said key shaft in an angular position in which the flat surface of the key portion is substantially at right angles to the inclined surfaces of the wedge members and a part of said fiat key surface projects from the inclined surface of the first wedge member and bears over its whole area extending substantially from said inclined surface as far as the circumference of said semi-cylindrical portion against said at surface of said abutment, whereby, owing to the closeness of said key shaft axis from said inclined surfaces, the major portion of the load on the key shaft is ltaken as a journaled load between said shaft and the recess in the first wedge member and a minor portion is applied to the shaft as a torque which tends to rotate the key shaft about its axis and is resisted by said locking means.

References Cited in the ile of this patent FOREIGN PATENTS 585,757 Great Britain Feb. 24, 1947 684,643 Great Britain Dec. 24, 1952 697,370 Germany Oct. l2, 1940 780,300 France Ian. 29, 1935 968,622 France Apr. 26, 1950 

